There are 21 main regions, in which of these regions your characters will start will be determined by their race , class , description , and background feats if if they have any (for background feats see above)
I am sorry but i will not reveal much about the world's history your characters will learn more depending from the region they start the ranks in knowledge skills and they will have the opportunity to uncover even more as they progress.
As for what you need to know: there was never a full out war between elves and dark elves, as a result Dark elves don't go by the title Drow instead sometimes they are called night elves also they don't suffer from the dark reputation they have in most other worlds yet they are still considered the most ruthless and vile of elvenkind, but that doesn't say much. underground dark elven cities are known to exist but that's all. Something other about dark elves is that Lolth goes by two faces one is Lolth the demon queen of chaos and the other is Arasanlee or Weaver the elven godess of Magic and fate.
The underground known as deep caves is full of undead and while they are not known to actually leave their underground lair is not unheard for them to attack the surface in great numbers.
There is also a general distrust to arcane magic (in some cases magic in general)
and unsupervised mages often find themselves being hunted by an organization known as ''Mage hunters".psionics are quite new power in this world and quite unknown too, most people consider psionic users freak-mages, many psion consider themselves that too while others prefer to believe they have master an even greater form of arcana and call themselves high-arcanists. Real masters of arcane arts who research onto psionics have come to understand there is not the slightest connection between arcana and this new power. Among their circles they tend to refer to psions as mind mages and keep an eye for people who show signs of psionic powers.There was a time were dragons were hunted near to extinction now most if not all of the surviving dragons live in Dalron along with humans. Dragon hunters still exist but they are only a shadow of their former glory
I should also mention that i have also empower some monsters with some "sense" abilities with most notable amongst them outsiders and dragons